The invention relates to a method for setting blind rivet elements in which the setting of the respective blind rivet element introduced into a pre-hole of the work piece and/or the formation of a rivet collar takes place in a setting stroke (SH) through the permanent deformation of a section of the blind rivet element by subjecting an end of the blind rivet element to a traction force by means of a traction element of a setting tool while simultaneously supporting another end of the blind rivet element on a support part of the setting tool counter to the traction force. Prior to forming the rivet collar the state of the disposition of the respective blind rivet element on the setting tool and/or the distance corresponding to this state between the blind rivet element and the tool support part is detected. The invention also relates to a setting tool for processing or setting the blind rivet elements.
Blind rivet elements, according to the invention, are primarily blind rivet nuts, but can also be other normally used blind rivet elements, such as blind rivets and blind rivet bolts.
The setting of blind rivet elements, according to the invention, means securing the respective blind rivet element introduced into a pre-hole of a work piece by riveting, i.e. by forming a rivet collar by applying a traction force through a traction element, through a traction mandrel to an area or an end of the blind rivet element that is remote from the rivet flange of the blind rivet element on which the blind rivet element is supported on a tool support part during setting. The rivet collar is formed through permanent deformation of a rivet element section. The rivet collar secures the blind rivet element against being pressed out and/or twisting in the work piece.
Setting of blind rivet elements in the form of blind rivet nuts takes place with the spin-pull method. In accordance with the spin-pull method the respective blind rivet nut is screwed with its nut or inner thread formed on one end of the blind rivet nut body onto the outer thread of a traction mandrel, i.e. by spinning it on. Securing of the blind rivet nut inserted into a pre-hole of a work piece takes place by pulling the traction mandrel while simultaneously supporting the blind rivet nut on the tool support part with its blind rivet nut end or rivet flange that is remote from the inner thread, namely deforming the rivet collar from a section of the blind rivet nut body not received in the pre-hole. Pulling of the traction mandrel takes place either until a pre-defined traction force is reached or until a pulling distance (setting stroke) defined by at least one stop is reached. Upon reaching the complete setting stroke, or the traction force, the traction mandrel is screwed out of the inner thread of the set blind rivet nut.
A frequent cause for faulty setting of blind rivet nuts in work pieces exists in the case of manual processing, but also in the case of automatic processing due to the fact that the traction mandrel is not completely screwed into the respective blind rivet nut, i.e. spinning of the blind rivet nut onto the traction mandrel is incomplete, namely so that the blind rivet nut and the rivet flange have an axial distance from the tool support part that exceeds a pre-defined tolerance range and/or the traction mandrel is received with its threads only partially in the inner thread of the blind rivet nut. During the setting process, i.e. during pulling of the traction mandrel, this produces first a pre-stroke, which takes place without deformation of the blind rivet nut body and in which the blind rivet nut is only brought to bear against the tool support part. If the maximum stroke of the traction spindle is pre-defined by at least one stop, the actual setting stroke available for setting is reduced, namely with the result that the actual setting stroke or the actual pulling distance is not sufficient for correct formation of the rivet collar. Furthermore, the incorrect or incomplete spinning on of the respective blind rivet nut onto the traction mandrel has the disadvantage that the latter engages with only a reduced axial length in the inner thread of the blind rivet nut, resulting in stripping or damage to said inner thread, namely in particular also if the maximum stroke or pulling distance of the traction mandrel is not limited by stops, but instead the setting process is controlled by the traction force exerted on the respective blind rivet nut.
Equivalent or similar problems also occur during setting of other blind rivet elements, which during blind riveting likewise are secured in the work piece with their rivet flange bearing against a tool support part by the traction force exerted by a traction element of the blind rivet tool to a traction mandrel or rivet mandrel of the blind rivet element, thus forming a rivet collar. Here again in case of incorrect disposition of the respective rivet element on the blind riveting tool, i.e. in case of a distance between the rivet flange and the tool support part exceeding a pre-defined tolerance range, this will result at least in incomplete formation of the rivet collar.
Up to now, incorrectly set blind rivet elements must be removed and/or repaired in a time-consuming process.
It is an object of the invention is to present a method that avoids the aforementioned disadvantages and in which the setting process is discontinued or paused or a correction of the setting stroke takes place in advance, i.e. before actual setting, if the respective blind rivet element is not correctly disposed on the blind riveting tool, i.e. its distance from the tool support part exceeds a pre-defined tolerance range.